This proposal is primarily focused on delineating the antigens relevant for protective immunity against leishmaniasis and clinical diagnosis of the disease (i.e., Kala-azar) as well as developing a further understanding of the biology of the parasite (i.e., its survival within its insect and mammalian hosts). The projects will involve the disciplines of biology, immunology, molecular biology and biochemistry. Monoclonal antibodies and molecular biology techniques will be used to identify and isolate molecules (stage specific and protective) of Leishmania. The specific aims of the proposal are: 1. Development of a reliable, specific serological diagnostic assay for visceral leishmaniasis. 2. Identification of antigens protective against infection with Leishmania donovani. 3. Further production of amastigote specific monoclonal antibodies to the amastigote stage. 4. Biochemical, biological and molecular biological characterization of stage-specific antigens (promastigote and amastigote) of Leishmania. 5. Evaluation of stage-specific antigens effectiveness of producing protective immunity in in vivo model systems. 6. Elucidation of mechanisms involved in protective immunity produced to both stage specific and cross-reactive antigens. 7. Analysis of Leishmania antigens on infected macrophages.